CREATE FOREIGN DATA WRAPPER

Name

Synopsis

Description

CREATE FOREIGN DATA WRAPPER creates a
new foreign-data wrapper. The user who defines a foreign-data
wrapper becomes its owner.

The foreign-data wrapper name must be unique within the
database.

Only superusers can create foreign-data wrappers.

Parameters

name

The name of the foreign-data wrapper to be created.

VALIDATOR valfunction

valfunction is the name
of a previously registered function that will be called to
check the generic options given to the foreign-data
wrapper, as well as to foreign servers and user mappings
using the foreign-data wrapper. If no validator function or
NO VALIDATOR is specified, then
options will not be checked at creation time. (Foreign-data
wrappers will possibly ignore or reject invalid option
specifications at run time, depending on the
implementation.) The validator function must take two
arguments: one of type text[], which
will contain the array of options as stored in the system
catalogs, and one of type oid, which
will be the OID of the system catalog containing the
options. The return type is ignored; the function should
indicate invalid options using the ereport() function.

OPTIONS ( option 'value' [, ... ] )

This clause specifies options for the new foreign-data
wrapper. The allowed option names and values are specific
to each foreign data wrapper and are validated using the
foreign-data wrapper library. Option names must be
unique.

Notes

At the moment, the foreign-data wrapper functionality is very
rudimentary. The purpose of foreign-data wrappers, foreign
servers, and user mappings is to store this information in a
standard way so that it can be queried by interested
applications. One such application is dblink; see Section
F.8. The functionality to actually query external data
through a foreign-data wrapper library does not exist yet.

There is currently one foreign-data wrapper validator function
provided: postgresql_fdw_validator,
which accepts options corresponding to libpq connection parameters.

Compatibility

CREATE FOREIGN DATA WRAPPER conforms
to ISO/IEC 9075-9 (SQL/MED), with the exception that the
VALIDATOR clause is an extension and the
clauses LIBRARY and LANGUAGE are not yet implemented in
PostgreSQL.

Note, however, that the SQL/MED functionality as a whole is
not yet conforming.